Electricity Cables From Street To House Underground

[haveaniceday]

Does anyone have any rel life experience in Thailand putting mains electricity cables under ground to the house?

To avoid ugly cables running across the property, I am guessing we would need about 100m of cable form the road to the house, I am happy enough with the initial cable up in the air along a boundary, but would like to put the last 50m underground.

I remember seeing the 4 inch thick black pipes in Bangkok with cable in them. It is normal in more developed countries, I can't see any reason why it should be so difficult. Anyone we have asked so far, just say, 'mai me'.

Have a nice day.

[stgrhe]

You should use a double-insulated cable, type NYY for underground installation and run the cable in a PE pipe. The PE pipe is most likely the 4" pipe you are referring to.

The number of cores will depend on whether you have a single-phase or a three-phase installation, two for the former and four for the latter. The cable size, i.e. the core areas, will depend on the cable length and the maximum current usage, which is defined by the rating of your main circuit breaker e.g. 100A.

This is how you calculate the cable size:

How to size the mains cable?

Physical Facts

The cable resistance per metre per mm² at 20^°C [T₁] for copper (Cu) is: 0.018 ohms (Ω) [R₁]

The temperature coefficient ρ (rho) for copper is: 0.004

Example

Main voltage supply: 220V [V]

Maximum Demand: e.g. 100A

Distance between transformer and distribution board: 100*) metres [L]

Estimated ground temperature (where cable shall run): 25^°C [T]

Maximum allowed voltage drop: 5% [V_d]

Sought cable area: [X] (mm²)

Total Resistance [R]

R = L x 2 [R₁ + ρ (T – T₁)]

R = 100 x 2 [0.018 + 0.004 (25 – 20)]

R = 7.6 Ω (per mm²)

Sought Cable Area [X]

I x R x 100 100 x 7.6 x 100

X = ------------------ ===> X = ------------------------ ===> X = 69 mm²

V_d x V 5 x 220

Result

For a maximum voltage drop across the mains cable the core area of the cable must be minimum 69 mm² ===> chose a 70 mm² cable (standard size).

*) The calculated length [L] is multiplied by 2 as the current flows both ways.

Edited July 20, 2011 by stgrhe

[canopy]

Does anyone have any rel life experience in Thailand putting mains electricity cables under ground to the house?

Yes, I did this recently and am very happy with it.

To avoid ugly cables running across the property

Not only are the lines, poles, and rigging an eyesore, but they also get in the way of landscaping. I come from an area outside Thailand where underground services are standard so these disadvantages are very noticeable to me and not doing it was basically unthinkable.

Anyone we have asked so far, just say, 'mai me'.

I designed and installed myself as no one from electricians to shops to PEA was familiar with proper processes or specifications and I wanted it done right. I received input here in a thread titled "minimal electricity setup". But to be brief, I buried NYY cable directly. No conduit is required in the trench as NYY is suitable for burial but you do need conduit on the up stands. NYY cable may not be available in many normal electrical shops but can be found abundantly in chinatown in bangkok. NYY is roughly double the price of aerial cable, but it should stay put as the work required to dig it out is immense compared to snipping a cable off a pole.

A few other suggestions. One is drop a suitable phone cable in while you are at it in case that might be needed in the future. Also on a run that far make sure you run a voltage drop calculator to size your cables properly.

[Crossy]

Result

For a maximum voltage drop across the mains cable the core area of the cable must be minimum 69 mm² chose a 70 mm² cable (standard size).

OR

Plug the requirements into one of the many online cable calculators.

This one at Doncaster Cables http://www.doncastercables.com/cableCalculator.asp suggests a 50mm² cable is appropriate for 100m @ 100A.

[katabeachbum]

did underground for 15 houses in 2006

we followed PEAs requirements, up to 100 meters 100A one phase, 35mm2 copper

either in yellow pvc pipes or in the black PA tubes

my 2 houses in this Moo Baan is at 40 and 60 meters, and not much drop in Voltage with 100A in 35mm2 copper

while installing, be aware of copper thieves. They even steel cable while connected to meter

[haveaniceday]

The Black PA tubes, anyone know what they are called in Thai?

Also, thinking about it, would prob be about 120m by the time followed the boundary around or missed ponds etc, we are talking a different more expensive cable for the underground, the first 50m would actually be strung on poles most likely regardless, is it possible to join the wires at the 50 m mark at the point they go into the ground? Would this join just be asking for trouble ? Am I thinking electrical solutions like a Thai wiring "expert" on this one ? LOL

Very roughly, just so I can think about this in a more realistic way, does anyone know the price of 70mm cable normal cable?

Underground cable

PA tubes?

Thanks

[Crossy]

Before going off and getting cable etc, do a rough maximum demand check and also determine what size supply MEA / PEA will be able to provide. No point cabling up for a 100A supply if they can only do a 15/45 (45A fused at 63A) for which a smaller size will do.

The above will also give you an idea if you're going to need 3-phase to provide for your demands.

How remote are you, that 50m on poles could be a magnet for copper thieves so consider Aluminium cable which is also rather cheaper. There are issues with Al cable but on the whole it may be worth the extra hassle.

[canopy]

we followed PEAs requirements, up to 100 meters 100A one phase, 35mm2 copper

Have you noticed this size does not agree by a long shot with what has been calculated here for the same parameters?

[stgrhe]

we followed PEAs requirements, up to 100 meters 100A one phase, 35mm2 copper

Have you noticed this size does not agree by a long shot with what has been calculated here for the same parameters?

Agree, the law of physics do no change because PEA provide odd information, provided this information is not based on a rather high voltage drop calculation.

[haveaniceday]

Thailand and the PEA is the HUB for world standards and wiring safety

[katabeachbum]

we followed PEAs requirements, up to 100 meters 100A one phase, 35mm2 copper

Have you noticed this size does not agree by a long shot with what has been calculated here for the same parameters?

yep, and thats why I posted Phuket PEA info. Up to OP to choose according to his max demand, available max meter size in area, and consider budget

BTW Phuket PEA did in 2006 not accept underground aluminum

[electau]

Single phase 100A max demand for a route length of 100 meters 70sqmm copper for 3% voltage drop.

For 5% voltage drop 50sqmm copper.

Ref AS3000

Do a max demand calculation first and then approach the PEA for their requirements.

[canopy]

Up to OP to choose according to his max demand, available max meter size in area, and consider budget

Designing a system for "budget" here seems to imply it is acceptable for a house to go into a brownout condition every time electrical use is high resulting in impaired functionality. For a 100M run with 35mm2 cable, a 100A MCB is too large. The cable cannot safely supply that much power.

[electau]

Up to OP to choose according to his max demand, available max meter size in area, and consider budget

Designing a system for "budget" here seems to imply it is acceptable for a house to go into a brownout condition every time electrical use is high resulting in impaired functionality. For a 100M run with 35mm2 cable, a 100A MCB is too large. The cable cannot safely supply that much power.

80 amps over that route length of 100M using 35sqmm cable for a voltage drop of 5%. The MCB would have a rating of 80A max. Voltage drop is the determining factor. For 3% voltage drop a larger size of cable would be required.

[katabeachbum]

Up to OP to choose according to his max demand, available max meter size in area, and consider budget

Designing a system for "budget" here seems to imply it is acceptable for a house to go into a brownout condition every time electrical use is high resulting in impaired functionality. For a 100M run with 35mm2 cable, a 100A MCB is too large. The cable cannot safely supply that much power.

Central Government approved Moo Baan use 8mm2 for up to 30meters distance from 15/45A meter with MCB 63 Amp

Welcome to Thailand

[canopy]

Wow, the PEA advice never ceases to amaze. I was wondering if it was just my area but now see it is widespread. What a travesty to the majority who must believe they are getting sound advice. In my experience the PEA get even the simplest things wrong. Of course they recommended the wrong cable size that was too small for my application, but I just couldn't believe it when they drilled holes through the side of my weatherproof box where rain runs down the wires and straight onto the breaker. On another occasion I discussed grounding with them because I wanted to be sure I would meet their requirements only to find their requirements so weak that I mentioned the minimum US specifications I planned to use and they shrugged it off with "the dirt is different here". Shortly after that I bought an electrical panel and it had an installation sheet written completely in Thai that specified a ground that matched my specifications rather than the weaker PEA recommendation. I could go on and on. Beware PEA recommendations can be unsound and unsafe which is very unfortunate when the subject is high voltage wiring.

[happyjune]

I am very curious,

Post #12

"Single phase 100A max demand for a route length of 100 meters 70sqmm copper for 3% voltage drop.For 5% voltage drop 50sqmm copper".

What is an acceptable % drop ?

[transam]

Mine is under ground with no probs BUT my pals house, which was built by the same builders had a prob after a couple of years. When it rained they got an electric shock walking up the driveway through bare feet . Soooooo, he had to re-wire over head from the street pole.

When the electrician went into the roof space he got a shock off the suspended ceiling frame work. Just hope my place didn't have the same electrician eh, though two big fancy light fittings have crashed to the floor.

[Crossy]

I am very curious,

Post #12

"Single phase 100A max demand for a route length of 100 meters 70sqmm copper for 3% voltage drop.For 5% voltage drop 50sqmm copper".

What is an acceptable % drop ?

The UK regs permit up to 5% from source of supply for lighting circuits.

Usually one would divide that between the submain (incoming cable from meter to distribution board) and the final circuit (distribution board to fittings). Much depends upon how long your incoming feed is, but 3% would be good, 5% pushing the envelope. But do remember that you don't do these calculations using the absolute maximum demand but on the diversified demand, suddenly it becomes more complex.

Simple answer, 5% at maximum demand should be OK for 90% of the time, the other 10% may result in lights dimming when the pump starts or similar effects.

[stgrhe]

Wow, the PEA advice never ceases to amaze. I was wondering if it was just my area but now see it is widespread. What a travesty to the majority who must believe they are getting sound advice. In my experience the PEA get even the simplest things wrong. Of course they recommended the wrong cable size that was too small for my application, but I just couldn't believe it when they drilled holes through the side of my weatherproof box where rain runs down the wires and straight onto the breaker. On another occasion I discussed grounding with them because I wanted to be sure I would meet their requirements only to find their requirements so weak that I mentioned the minimum US specifications I planned to use and they shrugged it off with "the dirt is different here". Shortly after that I bought an electrical panel and it had an installation sheet written completely in Thai that specified a ground that matched my specifications rather than the weaker PEA recommendation. I could go on and on. Beware PEA recommendations can be unsound and unsafe which is very unfortunate when the subject is high voltage wiring.

That is regrettably my experience too. The local PEA in Pran Buri couldn't even tell me what type of grid they had, and when pressed for an answer they said TN-C. After investing the supply side myself I found out that we in fact have a TT-grid.

Also during the installation of our moo baan's transformer PEA ran two aluminium wires, one from the transformer's chassis and one from the secondary winding's neutral point, to the ground and then about two metres underground on a depth of half a feet. That was the transformer's earthing! Yeh! No wonder why there are so many problems with the electricity here in Thailand.

[electau]

I am very curious,

Post #12

"Single phase 100A max demand for a route length of 100 meters 70sqmm copper for 3% voltage drop.For 5% voltage drop 50sqmm copper".

What is an acceptable % drop ?

Australian Standard AS3000 the max voltage drop permitted is 5% from the point of connection of supply to the consumers mains to any point of utilisation within the electrical installation.

Generally 3% is allowed for in the consumers mains and sub mains and 2% in the final subcircuits.

　

[electau]

Up to OP to choose according to his max demand, available max meter size in area, and consider budget

Designing a system for "budget" here seems to imply it is acceptable for a house to go into a brownout condition every time electrical use is high resulting in impaired functionality. For a 100M run with 35mm2 cable, a 100A MCB is too large. The cable cannot safely supply that much power.

Central Government approved Moo Baan use 8mm2 for up to 30meters distance from 15/45A meter with MCB 63 Amp

Welcome to Thailand

Voltage drop for a max demand of 45amps using 10sqmm copper over a route length of 30meters is 2.6%

Ther is no size of 8 sqmm in metric cables.

The max demand is actually 63amps if you use the rating of the MCB. In this case the percentage voltage drop would be 3.7%.

Edited July 28, 2011 by electau

[David006]

Stepping back a little: While it is interesting,commendable and perhaps helpful applying western voltage drop formulae to Thai installations, is it not all relative to the supplied voltage? What is the "typical" voltage at the meter...I have noticed it is all over the map below 240v.?

Are not most appliances rated 220-240v? So if you are lucky enough to have an average say of 230v .. theoretically up to 10% to play with?

Maybe I am missing something??

Anyone know what size the electric cos aerial cable feeder is...judging by many posts it may well be somewhat undersized by western calculations...in which case....pearls before swine?

Rotted sisal rope never got any stronger by splicing a length of hi tensile nylon to the end ..lol

[electau]

Stepping back a little: While it is interesting,commendable and perhaps helpful applying western voltage drop formulae to Thai installations, is it not all relative to the supplied voltage? What is the "typical" voltage at the meter...I have noticed it is all over the map below 240v.?

Are not most appliances rated 220-240v? So if you are lucky enough to have an average say of 230v .. theoretically up to 10% to play with?

Maybe I am missing something??

Anyone know what size the electric cos aerial cable feeder is...judging by many posts it may well be somewhat undersized by western calculations...in which case....pearls before swine?

Rotted sisal rope never got any stronger by splicing a length of hi tensile nylon to the end ..lol

All calculations are based on the nominal voltage at the point usually where the service line connects to the consumers mains.

This voltage in Thailand is 220V for single phase. The difference between 220 to 240 nominal is negligible in practice.

It is the responsibility of the MEA/PEA to maintain their supply voltage at the legislative standards with a fixed variance + or - % of the nominal voltage.

AS3000 for instance use 230V as the basis for calculation but 240V was used prior to harmonisation with the IEC. The actual supply voltage in practice to the consumers terminals did not change and voltages is generally 235 to 245V.

Yes, one would agree that voltage regulation is poor in Thailand in practice.

Negligible in practice. 5% of 240 volts is 12 V. 5% of 230 volts is 11.5V. 5% of 220V is 11.0V.

Calculations are based on those voltages irrespective of the actual voltage recorded at any time.

　

Edited July 29, 2011 by electau

[David006]

Stepping back a little: While it is interesting,commendable and perhaps helpful applying western voltage drop formulae to Thai installations, is it not all relative to the supplied voltage? What is the "typical" voltage at the meter...I have noticed it is all over the map below 240v.?

Are not most appliances rated 220-240v? So if you are lucky enough to have an average say of 230v .. theoretically up to 10% to play with?

Maybe I am missing something??

Anyone know what size the electric cos aerial cable feeder is...judging by many posts it may well be somewhat undersized by western calculations...in which case....pearls before swine?

Rotted sisal rope never got any stronger by splicing a length of hi tensile nylon to the end ..lol

All calculations are based on the nominal voltage at the point usually where the service line connects to the consumers mains.

This voltage in Thailand is 220V for single phase. The difference between 220 to 240 nominal is negligible in practice.

It is the responsibility of the MEA/PEA to maintain their supply voltage at the legislative standards with a fixed variance + or - % of the nominal voltage.

AS3000 for instance use 230V as the basis for calculation but 240V was used prior to harmonisation with the IEC. The actual supply voltage in practice to the consumers terminals did not change and voltages is generally 235 to 245V.

Yes, one would agree that voltage regulation is poor in Thailand in practice.

thanks for that..I think I would be happy if the bloody power would stay on for a reasonable period!..Sometimes it is off for 6-8 hours on a perfectly sunny day...other times it flicks on and off several times a day...hate to think of the spikes! ...seen 3w fluorescent lamps look like 50w sometimes...so I never leave TV etc on standby...go figure

[katabeachbum]

Up to OP to choose according to his max demand, available max meter size in area, and consider budget

Designing a system for "budget" here seems to imply it is acceptable for a house to go into a brownout condition every time electrical use is high resulting in impaired functionality. For a 100M run with 35mm2 cable, a 100A MCB is too large. The cable cannot safely supply that much power.

Central Government approved Moo Baan use 8mm2 for up to 30meters distance from 15/45A meter with MCB 63 Amp

Welcome to Thailand

Voltage drop for a max demand of 45amps using 10sqmm copper over a route length of 30meters is 2.6%

Ther is no size of 8 sqmm in metric cables.

The max demand is actually 63amps if you use the rating of the MCB. In this case the percentage voltage drop would be 3.7%.

Land & House, Baan Parichart all 160 houses have 8mm2 from meter to MCB

[Crossy]

Land & House, Baan Parichart all 160 houses have 8mm2 from meter to MCB

As Electau notes 8mm² is not a standard size, is it possibly imported 8 AWG (which just happens to be about 8mm²)?

Bangkok Cable are rating their 10mm² at 65-80A depending upon fixing and location, significantly greater than the UK and Aussie ratings of 40-55A.

I think I'll stick to the UK ratings.

[electau]

Land & House, Baan Parichart all 160 houses have 8mm2 from meter to MCB

As Electau notes 8mm² is not a standard size, is it possibly imported 8 AWG (which just happens to be about 8mm²)?

Bangkok Cable are rating their 10mm² at 65-80A depending upon fixing and location, significantly greater than the UK and Aussie ratings of 40-55A.

I think I'll stick to the UK ratings.

Under AS3008 two single core 10sqmm V75 cables run directly buried configuration can be rated up to 94 amps and XPLE up to 105 amps. But these are for very short route lengths in meters. And of course are subject to voltage drop requirements. Would not likely be used in practice. And certainly not for consumers mains for residential purposes.

No wonder Thailand has voltage drop problems.

Edited July 31, 2011 by electau

[haveaniceday]

Crossys post number 4, the link is dead, the new link is http://www.doncastercables.com/technical/cable_calculator

Crossy talks about 100 amps, all the PEA meters around here are 5(15) AMP or 15(45)AMP. I have looked at a hose with about 4 or more air cons and it has a 15AMP meter. I am looking 115-130m depending on the route I take. Running cable direct would be much more ugly.

For a 5% drop the recommended cable goes form 50mm to 70mm at 115m for 100 AMP.

The discussion has been 100 AMP, well is it 100AMP or 15 AMP ? I a m boffon on this !!!!

I thought brown outs were really nasty for motors and compressors in fridges and aircons ?

I am trying to get a price form the local idiots, so far the two experts have insisted that a 35mm cable running 130m is all good. Still they didn't give even an idea of price.

I have had a gut full to be honest of the mass retardation of this place.

[haveaniceday]

Anyone got any idea in Thailand how much it cost for 50mm or 70mm to run 100m?